DETROIT — Cadillac is expecting the go-ahead to build a new flagship based on the same platform as the Ciel concept car.

General Motors is expected to give the go-ahead to Cadillac’s flagship Omega project before year-end, according to senior sources, the maker’s top management encouraged by the overwhelmingly positive reaction of the luxury division’s new Ciel concept vehicle.

It’s unclear whether a convertible or sedan version based on the big Omega platform would be first to market, but there is a clear consensus that Caddy needs a super-premium model if it is to have a chance of regaining its position as “standard to the world,” as its long-time ad slogan declared.

Omega would be just one in a wide range of new offerings that would be added to the Cadillac line-up, officials told TheDetroitBureau.com, helping the once-dominant marque fill in the so-called “white space” between its current model mix. That will include not only a new plug-in hybrid — but very likely some more conventional hybrid-electric models, as well.

Adding a “flagship” to the line-up is critical, said Cadillac design director Clay Dean during the Ciel’s first public showing in Detroit. The concept convertible was first revealed, earlier this month, during the run-up to the annual Pebble Beach Concours d’Elegance, where it generated “wows” from both potential customers and the gathered media.

The decision to show the prototype was strongly influenced by the need to make a formal decision on the Omega project, which would target a market segment above the coming Cadillac XTS — itself the replacement for the largely unloved Caddy STS sedan. While there is strong support for the super-premium project there was concern whether the public would accept the idea of something so bold.

“We do have this residual positive sentiment but the fact is that we’re not relevant for many consumers,” said Don Butler, the division’s marketing chief.